Rotary fluid cylinder for self-centering chuck

ABSTRACT

A rotary cylinder for a self-centering chuck has two valve units in its interior to prevent escape of fluid from the cylinder should the pressure fail in the conduit supplying fluid to keep the chuck jaws locked. The valve units each comprise inner and outer tubes passing through the piston, an annular space being defined between them, the inner tube communicating with a conduit passing through the cylinder body, an annular ridge on the outer surface of the inner tube, a hole in the wall of the inner tube adjacent the ridge and on a first side of it, and holes in the ends of the outer tube to communicate with the chambers into which the piston divides the cylinder. A closure member is located between the tubes on the second side of the ridge, being biased towards the ridge. A control member is sealingly slidable in the first part between the tubes and has a projection which can, under a pressure differential, move the closure member off the ridge to permit fluid to flow past the ridge and the closure member and thus enter the chamber beyond the closure member.

Uted States atent' [1 1 Pinto ROTARY FLUID CYLINDER FOR SELF-CENTERINGCHUCK [75] Inventor: Franca Fint0,Turin,Italy [73] Assigneez Mario finto S IPLAJTurin,

Italy [22] Filed: Apr. 7, 1971 [21] Appl. No.: 132,025

[30] Foreign Application Priority Data May 9, 1970 Italy 68605 A/70 [52]US. Cl 91/420, 91/422, 92/106,

- 279/4 [51] Int. Cl. FlSb 11/08, FlSb 13/042 [58] Field of Search91/420, 422, 222, 91/228; 279/4; 92/106 [56] References Cited UNITEDSTATES PATENTS 3,364,823 l/1968 Benjamin et al 91/420 3,369,464 2/1968Blattry 91/420 3,411,415 ll/l968 Benjamin et al... 91/420 3,451,3146/1969 Smrekar 279/4 3,641,875 2/1972 Kodallc 91/420 PrimaryExaminerPaul E. Maslousky Att0rney-Sughrue, Rothwell, Mion, Zinn &Macpeak [57] ABSTRACT A rotary cylinder for a self-centering chuck hastwo valve units in its interior to prevent escape of fluid from thecylinder should the pressure fail in the conduit supplying fluid to keepthe chuck jaws locked. The valve units each comprise inner and outertubes passing through the piston, an annular space being defined betweenthem, the inner tube communicating with a conduit passing through thecylinder body, an annular ridge on the outer surface of the inner tube,a hole in the wall of the inner tube adjacent the ridge and on a firstside of it, and holes in the ends of the outer tube to communicate withthe chambers into which the piston divides the cylinder. A closuremember is located between the tubes on the second side of the ridge,being biased towards the ridge. A control member is sealingly slidablein the first part between the tubes and has a projection which can,under a pressure differential, move the closure member off the ridge topermit fluid to flow past the ridge and the closure member and thusenter the chamber beyond the closure member.

5 Claims, 3 Drawing Figures PATENTEUJUL3 1 I973 SHEEI 1 0F 3 INVENTOR mogm m N wln nfl M M Mi.

SHEET 2 0F 3 PATENTEUJULa 1 1915 ROTARY FLUID CYLINDER FORSELF-CENTERING CHUCK This invention concerns rotary fluid cylinders forthe control of self-centering chucks for lathes.

As is known, in some types of self-centering lathe chucks, the jawswhich lock the work piece are controlled by oscillating levers, housedin seats formed in the chuck body. The levers are in turn all controlledby an axial tension member which is actuated by a doubleacting hydrauliccylinder, fixed to one end of the rotary shaft of the chuck.

The hydraulic cylinder is connected by flexible conduits to a source offluid under pressure in such a way that it is possible to move theoscillating levers, and therefore the jaws in both directions.

Usually the conduits for supplying and recovering the fluid underpressure are provided with security valves, adapted to intervene to stopthe circulation of fluid when a breakdown takes place in the hydraulicsystem. Because such valves are located outside the cylinder, they canintervene effectively for all breakdowns which occur upstream of thecylinder, namely at points located between the valves and the source offluid under pressure.

On the other hand, for breakdowns which occur downstream of such valves,no practical remedy exists. Such a situation can be very dangerous sincea sudden fall of pressure in the hydraulic circuit can cause looseningof the jaws and the violent expulsion of the workpiece under centrifugalforce.

Another drawback is that the tension member which controls the jaws asdifficult to regulate because of the different lengths of the chucks andof the heads of the lathes. This makes it very laborious to set themachine, and hinders the interchangeability of the cylinders in suchlathes.

Moreover in rotary cylinders of known type a significant heating of thecylinder takes place, caused by the high pressures of the fluid incirculation.

The invention has the object of overcoming the drawbacks mentioned aboveby providing a rotary hydraulic cylinder which has high safetycharacteristics as regards possible drops in pressure in the circuit,and which is able in such circumstances to prevent release of the jaws.

Another object of the invention is to provide a rotary hydrauliccylinder which allows convenient, easy and precise regulation of thetension member which connects the cylinder to the self-centering chuck.

Another object is to provide a rotary cylinder in which eccessiveheating of the cylinder is effectively combated.

The invention provides a rotary fluid cylinder for the control of aself-centering chuck, the cylinder containing a piston that is adaptedto be connected to a tension member extending into the chuck, the pistondividing the cylinder into two chambers, and including a conduit forfluid leading into each chamber, and valve means located within thecylinder and adapted, when fluid is supplied under pressure througheither one of the conduits, to permit the flow of fluid through thatconduit and the discharge of fluid through the other conduit; the valvemeans being further adapted, when the pressure in the conduit throughwhich fluid is supplied drops below a predetermined value, to close thatconduit.

In the drawings:

FIG. 1 is a schematic side view in elevation, partly sectioned, of alathe head which incorporates a rotary hydraulic cylinder according tothe invention to control a self-centering chuck;

FIG. 2 is an axial section on a reduced scale of the cylinder of FIG. 1,and

FIG. 3 is a schematic axial section, on an enlarged scale, illustratingthe functioning of two valve units in corporated in the cylinder ofFIGS. 1 and 2.

A support 1 for a lathe head is provided with a self centering chuck 2whose jaws 3 are radially controlled by oscillating levers 4, housed inradial seats formed in the chuck. Each such lever has a short arm 4awhich engages a jaw 3, and a long arm 4b which is controlled by themovement of a grooved tubular head 5 carried by a tubular tension member6, housed slidably and coaxially in a hollow control shaft 7 whichcarries the chuck 2 at one end. The control shaft 7 is rotated by anexternal motor (not illustrated), which transmits movement to a controlpulley 8. The other end of the shaft 7 carries a rotary hydrauliccylinder 9, which has the task of controlling the axial movements of thetension member 6.

As seen in FIG. 2, the rotary hydraulic cylinder 9 comprises a cylinder10, closed at one end by a separate head 11 and provided its other endwith a tubular appendix 12 of reduced diameter. In the cavity of thecylinder 10 slides sealingly a piston 13, solidly fixed to a tubularmember 14 which, as described below, is connected to the tension member6. I

Fixed to the rear end (i.e., the end seen on the left in FIG. 2) of themember 14 is a tubular appendix I5 having a frusto-conical cavity whichtapers convergingly towards the chuck (i.e., towards the right in FIG.2). The appendix 15 is provided with external threading. With thisappendix co-operates an expansible collet 16 that is provided withspring sectors 16a and is internal threaded. This collet screws on to athreaded rear part 6a of the tension member 6 and is locked in thecavity of the appendix 15 by a ring nut 17, screwed on to the threadedexternal part of such appendix. The collet 16 is provided with notches16b accessible from outside the lathe head and which allow the collet tobe rotated. This causes screwing-on or unscrewing with respect to thetension member 6 and thus allows regulation of the axial position of thetension member 16 with extreme precision, in order to synchronize themovements of the piston 13 property with the movements of the levers 4which control the jaws 3 of the chuck. By fully screwing on the externalring nut 17 it is possible to lock the collet l6 angularly on thetension member, fixing the collet solidly with the member 14 of whichthe piston 13 forms part.

The tubular appendix 12 of the rotary cylinder 10 is surrounded by afixed shaped cowl 18, provided with an internal tubular part 18a whoseinternal surface is in sealing contact with the tubular appendix 12 ofthe cylinder 10. In the internal part 18a of the cowl l8 are formed twoannular manifolds 19 and 20, communicating (by passages not shown) withsupply and return conduits (not shown) for fluid under pressure andplaced in communication, by means of radial apertures in the appendix12, with two longitudinal conduits 21, 23 formed in the appendix 12.

The conduits 21 and 23 are controlled respectively by valve units 22 and24, so that the conduit 21, as will emerge more fully below, leads intoa chamber A of the cylinder and the conduit 23 leads into a chamber B.The valve units 22 and 24 are arranged longitudinally from end to end ofthe cylinder 10 and pass sealingly through the piston 13. These valveunits control the passage of fluid into and from the cylinder so thatfluid entering through the conduit 21 causes retraction of the piston,and when entering through the conduit 23 causes advance of the piston.

As seen in FIG. 3, each of the valve units 22,24 is similar to the otherand is mounted symmetrically with respect to the other, in such fashionas to ensure correct functioning when fluid enters the cylinder 10 ineither direction.

For the sake of simplicity only the valve unit 22 will be fullydescribed, corresponding components of the valve unit 24 beingidentified by corresponding reference numerals followed by a dash. 45

The valve unit 22 comprises a fixed outer tube 25 passing sealinglythrough the piston 13 and extending from end to end of the cylinder 10.It is provided near its ends with radial holes 26, 27 in its wall, whichholes communicate respectively with the two chambers A,B into which thecylinder is divided by the piston 13. Inside the outer tube 25 is afixed inner tube 28, arranged with radial clearance so that an annularspace is defined between the tubes 25, 28. The inner tube 28 has an openend which communicates with the conduit 21 in the cylinder 10, throughwhich fluid is shown by arrows to be entering. The tube 28 has a ridge30 on its outer surface, the ridge dividing the valve unit transverselyinto a first part and a second part. In the first part, adjoining theridge 30, is at least one hole 29 in the wall of the inner tube 28.

Also in the first part of the valve unit, between the tubes 25 and 28,is arranged a slidable cup-shaped control element 31, having a tubularprojection 32 which extends towards the second part of the valve andwhich is provided with radial apertures 33 and which, in one position,loosely surrounds the ridge 30. A radial extension 31a of the element 31slides sealingly in a zone 25a of greater diameter of the outer tube 25.The radially inner surface of the element 31 slides sealingly on theinner tube 28.

In the second part of the valve unit is disposed a slidable cup-shapedmember 34, which is biased by a spring 35 reacting against the cylinderhead 11 to form a closure member. The member 34 is provided, on its facedirected towards the control element 31, with an annular seal 36,adapted to co-operate with the ridge 30. The closure element 34 moreoverhas a plurality of radial apertures 38, which allow communicationbetween an annular space 37, defined by such member 34 and by the innertube 28, and a second annular space 39 defined by such member 34 and bythe outer tube 25.

In normal rest conditions, namely in the absence of pressure, the spring35, as illustrated in FIG. 2, maintains the closure member 34 in aposition in which it contacts the annular ridge 30 on the inner tube 28,preventing flow of fluid from the conduit 21 to the chamber A of thecylinder.

The other valve unit 24 is arranged in a way such that its closuremember 34' abuts the ridge 30' to prevent fluid from passing from thechamber B of the cylinder, to the conduit 23, which is presumed for themoment to be an outlet conduit.

When fluid enters under pressure through the conduit 21, it passesthrough the holes 29 to act on the closure member 34, causing axialmovement of such member 34 towards the head 1 1, overcoming the biasingaction of the spring 35. In this way fluid is allowed to pass throughthe composite conduit formed by the conduit portion 21, space 37, theradial holes 38, the second space 39 and the radial holes 26 to reachthe chamber A of the cylinder. Acting in this chamber, the fluid causesretraction of the piston 13, i.e., movement towards the left in thedrawings.

At the same time, fluid which occupies the chamber B of the cylinder isdischarged through the conduit 23 in the cylinder 10. This flow ispossible because the pressure of the fluid in the chamber A-causesmovement towards the left of the control element 31' of the second valveunit 24, and the consequent movement in the same direction of theclosure member 34', against the action of the biasing spring 35'. Thisestablishes communication between the chamber B and the exterior conduit23 through the composite conduit 26', 39', 38', 37, 29, 28', 23.

If the supply pressure in the conduits 23 fails in this condition of thecylinder the two closure members 34, 34' of the two valve units,impelled by the respective springs 35, 35', move into the closedposition and prevent the passage of fluid both into the chamber Athrough the valve unit 22, and from the chamber B through the valve unit24. The piston 13 of the cylinder remains locked in the position it thenoccupies.

When the fluid circulates in the opposite direction to that describedabove and shown by arrows in FIG. 3, moving the piston 13 towards theright, the valve units 22, 24 act in a manner symmetrical with the modesdescribed above.

As is seen in FIG. 2, on one external annular wall of the cylinder 10 isfixed an annular element 40 of thin plate, in which are formed by meansof cutting and bending a plurality of radial fins 41, designed to createa ventilating effect to cool the cowl 18. Such fins draw in external airthrough an annular space 42 between the cylinder 10 and a cup-shapedappendix 18b of the cowl, and convey the air through frontal apertures43 towards the cowl, in a manner such as to impinge on its externalsurface and ensure cooling.

What we claim is:

1. A rotary fluid motor comprising a cylinder, a piston movable in saidcylinder and dividing the cylinder into two chambers, a conduit forsupplying fluid into each chamber, and valve means connected to saidconduits, said valve means being located within the cylinder andextending axially from one end of said cylinder to the other throughaperture means in said piston whereby, when fluid is supplied underpressure through either one of the conduits, said valve means permit theflow of fluid through that conduit and the discharge of fluid throughthe other conduit; the valve means being further adapted, when thepressure in the conduit through which fluid is supplied drops below apredetermined value, to close that conduit.

2. The cylinder of claim 1 in which the valve means comprises, for eachconduit, a closure member urged by biasing means towards a position inwhich it prevents flow through that conduit, the closure member beingadapted to yield to allow flow through that conduit when the pressure offluid in that conduit overcomes the biasing means; and further includingmeans adapted to cause the closure member controlling that conduit toyield when the pressure in the other chamber rises by a predeterminedvalue above that in the chamber into which that conduit leads.

3. The cylinder of claim 2, in which the conduits each include a conduitportion formed in a wall of the cylinder, and the valve means comprisestwo valve units each having an outer tube passing sealingly through thepiston and extending from end to end of the cylinder, an innter tubebeing contained with radial clearance in the outer tube to define aspace, the valve unit being transversely divided into a first and asecond part by an annular ridge on one of the tubes extending into saidspace, the first part of the inner tube being in communication with theconduit portion formed in the cylinder wall, and having an aperture inits wall adjacent the ridge to communicate with the space between thetubes, the outer tube having an aperture in its wall at each of its endsto communicate with the chamber at that end, the closure membercomprising an annular element located slidably in the second part of thevalve unit in the space between the tubes and having radial clearancewith respect to the tube on which the ridge is formed but being insealing contact with the other tube, a spring biasing the closure membertowards a position inwhich it bears sealingly against the ridge toprevent flow in the outer tube past the ridge; and further including acontrol element located slidably and sealingly between the tubes in thefirst part of the valve unit and having a projection extending towardsthe closure member, the projection being adapted, when the controlelement is moved toward the ridge, to engage the closure member and moveit away from the ridge to permit fluid to flow in the outer tube pastthe ridge.

4. The cylinder of claim 2, including a tubular member solidly connectedto the piston, the tubular member having at one end an internallyfrusto-conical appendix, a tension member being connected to the tubularmember by means of a frusto-conical expansible collet that is internallythreaded and is screwed on to a threaded portion of the tension member,the collet extending into the cavity of the appendix of the tubularmember and being secured by a locking ring which bears on the collet andis screwed on to a threaded part of the external surface of the appendixof the tubular member.

5. The cylinder of claim 2, including a fixed cowl surrounding a part ofthe cylinder with a space between the cylinder and cowl, and including aplurality of fins formed on the cylinder and extending into such space,and passages communicating with such space to permit the circulation airunder the fan effect of the fins.

1. A rotary fluid motor comprising a cylinder, a piston movable in saidcylinder and dividing the cylinder into two chambers, a conduit forsupplying fluid into each chamber, and valve means connected to saidconduits, said valve means being located within the cylinder andextending axially from one end of said cylinder to the other throughaperture means in said piston whereby, when fluid is supplied underpressure through either one of the conduits, said valve means permit theflow of fluid through that conduit and the discharge of fluid throughthe other conduit; the valve means being further adapted, when thepressure in the conduit through which fluid is supplied drops below apredetermined value, to close that conduit.
 2. The cylinder of claim 1in which the valve means comprises, for each conduit, a closure memberurged by biasing means towards a position in which it prevents flowthrough that conduit, the closure member being adapted to yield to allowflow through that conduit when the pressure of fluid in that conduitovercomes the biasing means; and further including means adapted tocause the closure member controlling that conduit to yield when thepressure in the other chamber rises by a predetermined value above thatin the chamber into which that conduit leads.
 3. The cylinder of claim2, in which the conduits each include a conduit portion formed in a wallof the cylinder, and the valve means comprises two valve units eachhaving an outer tube passing sealingly through the piston and extendingfrom end to end of the cylinder, an innter tube being contained withradial clearance in the outer tube to define a space, the valve unitbeing transversely divided into a first and a second part by an annularridge on one of the tubes extending into said space, the first part ofthe inner tube bEing in communication with the conduit portion formed inthe cylinder wall, and having an aperture in its wall adjacent the ridgeto communicate with the space between the tubes, the outer tube havingan aperture in its wall at each of its ends to communicate with thechamber at that end, the closure member comprising an annular elementlocated slidably in the second part of the valve unit in the spacebetween the tubes and having radial clearance with respect to the tubeon which the ridge is formed but being in sealing contact with the othertube, a spring biasing the closure member towards a position in which itbears sealingly against the ridge to prevent flow in the outer tube pastthe ridge; and further including a control element located slidably andsealingly between the tubes in the first part of the valve unit andhaving a projection extending towards the closure member, the projectionbeing adapted, when the control element is moved toward the ridge, toengage the closure member and move it away from the ridge to permitfluid to flow in the outer tube past the ridge.
 4. The cylinder of claim2, including a tubular member solidly connected to the piston, thetubular member having at one end an internally frusto-conical appendix,a tension member being connected to the tubular member by means of afrusto-conical expansible collet that is internally threaded and isscrewed on to a threaded portion of the tension member, the colletextending into the cavity of the appendix of the tubular member andbeing secured by a locking ring which bears on the collet and is screwedon to a threaded part of the external surface of the appendix of thetubular member.
 5. The cylinder of claim 2, including a fixed cowlsurrounding a part of the cylinder with a space between the cylinder andcowl, and including a plurality of fins formed on the cylinder andextending into such space, and passages communicating with such space topermit the circulation air under the fan effect of the fins.